The use of plastic components in combination with metal parts is common in the production of automobiles. Mixtures of resins and reinforcing materials are used as sheet molding compounds, SMCs, which are molded to form various shaped articles. Generally in applications requiring high quality painted surfaces, highly filled thermosetting SMCs have been used.
A long standing problem in providing reinforced composite structures resides in manufacturing structures which when painted provide a Class A finish. These structures such as automotive body panels must be capable of being processed in assembly plants with steel panels. They must be able to survive assembly plant conditions, painting and baking, where maximum metal temperatures can reach 200.degree. C. for as long as 30 minutes with surface coatings remaining firmly adherred to the substrate and retaining their Class A appearance. The body panels must have, after processing, an appearance that is comparable to the appearance of an adjoining pan made of steel. They must also have acceptable dimensional stability in order to maintain the highest quality fit and finish over wide temperature extremes found in various geographical market segments. When using SMCs, surface appearance problems such as "paint pops" occur due to emission of low molecular weight monomers in the thermosetting substrate, In addition an ever increasing concern is whether the material is readily recyclable during manufacture and in post manufacture use. For example, can the resin component be remelted or depolymerized. The thermosetting SMCs are not recyclable in the sense that they cannot be remelted or depolymerized.